Headaches, sore eyes and throat, nasal stuffiness, lethargy, skin complaints and an increase in airborne viral transmissions are all effects of a dry atmosphere. Dry air will suck moisture from all possible sources in the room including mucous membranes in the nose and throat, which are designed to protect us from infection. Moisture will also be drawn from any body tissue exposed during operations. This can cause premature drying and promote the formation of a scab from coagulated blood.

Perhaps more importantly in theatre is the effect of electrostatic shocks which build up below 40%RH. The uncomfortable, surprising jolts caused by a sudden 'static discharge can have potentially damaging and dangerous effects on surgery.

Consideration must also be given to the prevention of electrostatic sparks in relation to flammable anesthetic gases.

The humidity levels in maternity and obstetric departments should always be maintained as babies are particularly sensitive to a dry atmosphere. Also, low relative humidity can severely exacerbate the condition of patients with respiratory problems.

Many scientific studies have concluded that dry air has a direct impact on the transmission of airborne viruses and the length of time a virus stays infectious once airborne. Maintaining a hospital humidity at between 40-60%RH will reduce the spread of airborne viruses by inhibiting their ability to initially become airborne and the length of time they can survive once in the atmosphere.

Steam is a very popular solution in hospitals as it ensures the moisture being introduced is 100% safe and also due to the fact that there is often a ready supply of steam being used for sterilising purposes.